Federal and state governments have enacted progressive laws and regulations that impose ever-increasing restrictions on motor vehicles in the areas of exhaust emissions and improved fuel economy. For example, the California regulations include Super Ultra Low Emission Vehicle (SULEV) emission standards. It is noted that SULEV emission standards are particularly more stringent on hydrocarbon (HC) and nitrogen oxides (NOX) (e.g., nitric oxide (NO), nitrogen dioxide (NO2), nitrous oxide (N2O), and the like) emissions. Moreover, as this trend of increasingly restrictive emissions continues, Zero Emission Vehicle (ZEV) standards are eventually going to become the standard for exhaust gaseous emissions.
In order to meet exhaust gaseous emission standards, the exhaust gas emitted from internal combustion engines can be treated prior to emission into the atmosphere. Exhaust gases can be routed through an exhaust treatment device disposed in fluid communication with the exhaust outlet system of the engine, wherein the exhaust gas can be treated, for example, by reactions employing a catalyst. Examples of exhaust treatment devices include catalytic converters, catalytic absorbers/adsorbers (e.g., NOX adsorber), diesel particulate traps, non-thermal plasma conversion devices, oxidation catalyst devices, selective catalytic reduction (SCR) devices, and the like).
However, these exhaust treatment devices generally can have a temperature window in which the device is designed to optimally perform. During start-up conditions, exhaust gas can pass untreated through the exhaust treatment device, since the temperature in the exhaust treatment device can be below the temperature window. As such, start-up emissions can attribute a significant amount of the total allowed cumulative emissions. Further, during some instances of normal operation (e.g., idle conditions, low speed/load points, and the like), the temperature of the exhaust gas can drop below the temperature window of the exhaust treatment device, which can further allow exhaust gas to pass untreated through the exhaust treatment device.
Therefore, what are needed in the art are systems and methods that can allow rapid heating of the exhaust treatment device, and that can allow the desired temperature window of the exhaust treatment device to be maintained.